The two streams meet at a confluence. It takes many tributary streams to form a river. A river grows larger as it collects water from more tributaries. Streams usually form rivers in the higher elevations of mountains and hills. The areas of depression between hills or mountains are known as valleys.
The world's fastest production single piston engine aircraft produced in Great Britain, deployed from 1945 to 1953. Heavily Modified Sea Fury aircraft can be seen today as air racers. Heinkel He-162 562 mph. Arguably the fastest WW II jet fighter.
Another one of the fastest commercial airliners was the Concorde, which generally flew at a top speed of 1,330 miles (2,140.4 km) per hour. By comparison, the Boeing 747 operates at a cruising speed of about 550 miles (885.1 km) per hour. X-43. If having a pilot on board is not a criteria, then the X-43 is said to be the fastest airplane in the world.